Non-pressure solar water heater is a kind of solar water heater systems that the bellow collector directly connect with the above water tank. This solar water heaters do not need to run the pump to force and do not require pipeline connections between the collector and the tank . This is a simple and secure way to collect solar energy. This working principle of solar water heater is make it natural circulation between the water tank and the collector pipe . After the water in vacuum tube heated, natural convect into the water tank, meanwhile cold water in the tank flows down to the vacuum tubes, that is natural to run continuously to heat the water tank.